1. Field of the Invention
The present invention relates to compounds that inhibit serine/threonine kinases and are useful for treating hyperproliferative and neoplastic diseases by inhibiting signal transduction pathways, which are commonly overactive or overexpressed in cancerous tissue. The present compounds are selective inhibitors of ERK (extracellular-signal regulated kinase). The present invention further relates to methods for treating cancer or hyperproliferative diseases with compounds of the present invention.
2. Description of the State of the Art
The processes involved in tumor growth, progression, and metastasis are mediated by signaling pathways that are activated in cancer cells. The ERK pathway plays a central role in regulating mammalian cell growth by relaying extracellular signals from ligand-bound cell surface receptor tyrosine kinase (“RTK's”), such as ErbB family, PDGF, FGF, and VEGF receptor tyrosine kinase. Activation of an RTK induces a cascade of phosphorylation events that begins with activation of Ras. Activation of Ras leads to the recruitment and activation of Raf, a serine-threonine kinase. Activated Raf then phosphorylates and activates MEK1/2, which then phosphorylates and activates ERK1/2. When activated, ERK1/2 phosphorylates several downstream targets involved in a multitude of cellular events, including cytoskeletal changes and transcriptional activation. The ERK/MAPK pathway is one of the most important for cell proliferation, and it is believed that the ERK/MAPK pathway is frequently activated in many tumors. Ras genes, which are upstream of ERK1/2, are mutated in several cancers, including colorectal, melanoma, breast and pancreatic tumors. The high Ras activity is accompanied by elevated ERK activity in many human tumors. In addition, mutations of BRAF, a serine-threonine kinase of the Raf family, are associated with increased kinase activity. Mutations in BRAF have been identified in melanomas (60%), thyroid cancers (greater than 40%) and colorectal cancers. These observations indicate that the ERK1/2 signaling pathway is an attractive pathway for anticancer therapies in a broad spectrum of human tumors (Kohno, M. and J. Pouyssegur. “Pharmacological inhibitors of the ERK signaling pathway: application as anticancer drugs.” Prog. Cell Cycle Res. Vol. 5 (2003): pp. 219-224).
The ERK pathway has also been cited as a promising therapeutic target for the treatment of pain and inflammation (Ma, Weiya and Remi Quirion. “The ERK/MAPK pathway, as a target for the treatment of neuropathic pain.” Expert Opin. Ther. Targets. 9(4) (2005): pp. 699-713; and Sommer, Claudia and Frank Birklein. “Resolvins and inflammatory pain.” F1000 Medicine Reports. 3:19 (2011)).
Therefore, small-molecular inhibitors of ERK activity (i.e., ERK1 and/or ERK2 activity) would be useful for treating a broad spectrum of cancers, such as, for example, melanoma, pancreatic cancer, thyroid cancer, colorectal cancer, lung cancer, breast cancer, and ovarian cancer, as well as a treatment for pain and inflammation, such as arthritis, low back pain, inflammatory bowel disease, and rheumatism. Such a contribution is provided herein.